I would bet real cash money that many many people, including your coworkers, think that anyone who unironically uses the term "midwit" is completely and totally obnoxious.
Is he wrong though?
More cringe than obnoxious, but yeah.
People who uses the word "obnoxious" are also obnoxious. There are many unpleasant words, you have to use some of them and people don't like any of them.
Mweh, I'm not a native English speaker. It's a definitely existing archetype, though, just like "Spießbürger" points at a thing in German.